1. Field of the Invention
The present invention relates to a four-wheel-drive (4WD) all terrain vehicle (ATV).
2. Description of the Related Art
The 4WD all terrain vehicle includes a full-time 4WD type all terrain vehicle and a part-time 4WD type all terrain vehicle capable of switching between 2WD and 4WD. Either of them commonly comprises a brake system for braking front wheels and a brake system for braking rear wheels that are independent from each other.
Generally, a 2WD/4WD switching device comprises a dog clutch in a power transmission path for front-wheel-drive and is adapted to perform switching between 2WD and 4WD by engagement/disengagement of the dog clutch.
4WD all terrain vehicles travel over uneven roads, mountains, steep slopes, rough terrain, shore areas, and the like, and therefore, the brakes of 4WD are strongly applied more frequently than those of general vehicles. For this reason, even in the case of the 4WD all terrain vehicle comprising independent brake systems for front wheels and rear wheels, when the brake is applied only for the rear wheels to be locked, this sometimes locks the front wheels, which results in an uncomfortable braking operation.
In the case of the 4WD all terrain vehicle using the dog clutch as the 2WD/4WD switching device, switching operation during stopping is, in fact, impossible due to phase displacement in engagement between dog claws of the dog clutch.